/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.mock.web;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.Assert;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

/**
 * Mock implementation of the {@link javax.servlet.RequestDispatcher} interface.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Sam Brannen
 * @see MockHttpServletRequest#getRequestDispatcher(String)
 * @since 1.0.2
 */
public class MockRequestDispatcher implements RequestDispatcher {

    private final Log logger = LogFactory.getLog(getClass());

    private final String resource;


    /**
     * Create a new MockRequestDispatcher for the given resource.
     *
     * @param resource the server resource to dispatch to, located at a
     *                 particular path or given by a particular name
     */
    public MockRequestDispatcher(String resource) {
        Assert.notNull(resource, "Resource must not be null");
        this.resource = resource;
    }


    @Override
    public void forward(ServletRequest request, ServletResponse response) {
        Assert.notNull(request, "Request must not be null");
        Assert.notNull(response, "Response must not be null");
        Assert.state(!response.isCommitted(), "Cannot perform forward - response is already committed");
        getMockHttpServletResponse(response).setForwardedUrl(this.resource);
        if (logger.isDebugEnabled()) {
            logger.debug("MockRequestDispatcher: forwarding to [" + this.resource + "]");
        }
    }

    @Override
    public void include(ServletRequest request, ServletResponse response) {
        Assert.notNull(request, "Request must not be null");
        Assert.notNull(response, "Response must not be null");
        getMockHttpServletResponse(response).addIncludedUrl(this.resource);
        if (logger.isDebugEnabled()) {
            logger.debug("MockRequestDispatcher: including [" + this.resource + "]");
        }
    }

    /**
     * Obtain the underlying {@link MockHttpServletResponse}, unwrapping
     * {@link HttpServletResponseWrapper} decorators if necessary.
     */
    protected MockHttpServletResponse getMockHttpServletResponse(ServletResponse response) {
        if (response instanceof MockHttpServletResponse) {
            return (MockHttpServletResponse) response;
        }
        if (response instanceof HttpServletResponseWrapper) {
            return getMockHttpServletResponse(((HttpServletResponseWrapper) response).getResponse());
        }
        throw new IllegalArgumentException("MockRequestDispatcher requires MockHttpServletResponse");
    }

}
